export const base64ArrayBuffer = (arrayBuffer: ArrayBuffer) => {
  var base64 = "";
  var encodings =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  var bytes = new Uint8Array(arrayBuffer);
  var byteLength = bytes.byteLength;
  var byteRemainder = byteLength % 3;
  var mainLength = byteLength - byteRemainder;
  var a, b, c, d;
  var chunk;
  for (var i = 0; i < mainLength; i = i + 3) {
    chunk = (bytes[i] << 16) | (bytes[i + 1] << 8) | bytes[i + 2];
    a = (chunk & 16515072) >> 18;
    b = (chunk & 258048) >> 12; // 258048   = (2^6 - 1) << 12
    c = (chunk & 4032) >> 6; // 4032     = (2^6 - 1) << 6
    d = chunk & 63; // 63       = 2^6 - 1
    base64 += encodings[a] + encodings[b] + encodings[c] + encodings[d];
  }

  if (byteRemainder === 1) {
    chunk = bytes[mainLength];

    a = (chunk & 252) >> 2; // 252 = (2^6 - 1) << 2
    b = (chunk & 3) << 4; // 3   = 2^2 - 1
    base64 += encodings[a] + encodings[b] + "==";
  } else if (byteRemainder === 2) {
    chunk = (bytes[mainLength] << 8) | bytes[mainLength + 1];
    a = (chunk & 64512) >> 10; // 64512 = (2^6 - 1) << 10
    b = (chunk & 1008) >> 4; // 1008  = (2^6 - 1) << 4
    c = (chunk & 15) << 2; // 15    = 2^4 - 1
    base64 += encodings[a] + encodings[b] + encodings[c] + "=";
  }

  return base64;
};
